1. Field of the Invention
The present invention relates generally to the field of semiconductor manufacturing. More specifically, the present invention relates to handling of wafers in a wafer testing and/or processing procedure.
2. Description of the Related Art
The manufacture of integrated circuits begins with blank, unpatterned semiconductor wafers. These wafers undergo a number of sometimes critical process steps before being formed into the final integrated circuits form. The percentage of good integrated circuits from a particular fabrication lot is known in the industry as the yield percentage. A substandard wafer can affect the number of usable integrated circuits on a wafer (yield). It is therefore desirable to have a machine for testing wafers to ensure the wafers meet a customer""s standards to maximize wafer yield.
The testing of wafers is often accomplished by an automated process, in which robots continuously handle and test the wafers. Robot testing and handling tends to be more efficient than manual testing and handling of wafers, since robots can be much faster, more precise and less contaminating than human operators when handling wafers. In wafer handling processes, wafers are typically transported using carriers such as wafer cassettes and wafer pods. Pods differ from cassettes in that the pods typically are sealed to prevent contamination to the wafers enclosed therein.
Wafer carriers, sometimes known as xe2x80x9cboatsxe2x80x9d, contain batches of wafers. These carriers are then used to transport and hold the wafers inside furnaces as well as other equipment. These carriers are usually made of special materials, such as quartz and silicon carbide, which allow them to be used at the elevated temperatures inside furnaces while the wafers are being processed. Depending on the materials that carriers are made of, some of the existing carriers actually can change size over time at elevated temperatures. This can pose a huge problem to wafer handling automation. Additionally, these carriers are also limited in their useful temperature range. In certain processes, some commonly used materials cannot be used because the carrier would deform to an unusable state rather quickly. If the carriers change dimensionally after a period of time due to the stresses of the fabrication processes, they could prove to be unusable in the wafer loading equipment.
Wafers having a diameter of 8 inches are commonly used in the semiconductor industry for the manufacture of integrated circuits. The process chambers are usually configured for the 8xe2x80x3 wafers. However, customers sometimes need to use wafers having a diameter smaller than 8xe2x80x3 for special purpose. To process wafers smaller than the standard size, the process chamber size would have to be reconfigured. The process of reconfiguration could be time-consuming and risk-taking. Furthermore, the chances of contamination would be increased during the exposure of process chamber and robot to the ambient environment.
Therefore, the prior art is deficient in the lack of an effective method/apparatus for loading smaller diameter wafers or test chips for processing or testing in a standard process chamber without having to reconfigure the chamber size and robot calibrations. The present invention fulfills this long-standing need and desire in the art.
In one aspect, there is provided a wafer carrier which comprises a disk and a pocket, wherein the pocket is centered in the disk and holds the wafer.
In another aspect, there is provided a method of processing or testing a wafer for a semiconductor device. This method comprises the steps of placing the wafer in the wafer carrier described herein; loading the wafer carrier in a loadlock chamber; and transferring the wafer carrier from the loadlock chamber to a process chamber for processing or testing.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the embodiments of the invention given for the purpose of disclosure.